The referral of News Corporation's proposed acquisition of BSkyB to the Competition Commission ensures that no decision will be taken for at least six months. While the City had been expecting News Corp to withdraw its bid, Rupert Murdoch's surprise decision to tear up his promise to hive off Sky News will have earned him some goodwill in government circles.

The withdrawal of that promise, made earlier this year in order to avoid referral to the Competition Commission, left the culture secretary, Jeremy Hunt, free to pass on responsibility for deciding on the deal at a time of acute political pressure.

The commission inquiry will last a minimum of 24 weeks, and the regulator can take a further eight weeks to make a final decision. After that, the ball is back in the government's court. While most competition decisions were taken out of the hands of ministers with the 2002 Enterprise Act, on issues of national security, financial stability and the media they retain the right to have the final say.

The Competition Commission will deliver its verdict at the earliest just before Christmas and at the latest in mid-February, which means Hunt can put down this particular hot potato while the political temperature cools.

Those looking to predict the outcome will be able to get a flavour of the regulator's views by November. Provisional recommendations are normally issued between 16 and 18 weeks after the start of an inquiry. Within weeks, the commission is expected to outline the remit of its inquiry with an issues statement. That remit is already tightly defined. The European commission last year decided there was no reason to forbid the merger on competition grounds.

The Competition Commission will look simply at whether News Corp acquiring the 61% of Sky it does not already own would reduce the plurality of media ownership in the UK. When Ofcom looked into this question last year, it came to the conclusion that the merger would reduce plurality. There is no guarantee that the commission will come to the same conclusion.

In its statement on Monday, News Corp repeated its view that "taking into account the only relevant legal test, its proposed acquisition will not lead to there being insufficient plurality in news provision in the UK".

Media commentator and former Sky executive David Elstein, who was asked to give his views on the merger during last year's Ofcom inquiry, welcomed News Corp's decision to allow the bid to go to the Competition Commission.

"It depoliticises the situation," he said. "If you solve the plurality issue there is nothing else that stands in the way of the merger."

However, should both the Competition Commission and the culture secretary decide to block the bid, News Corp is free to appeal. This would delay the outcome by years rather than months.

There are precedents, and very close to home. In 2006, when James Murdoch was chief executive of BSkyB, he snapped up 17.9% of ITV's shares in a successful attempt to kill takeover plans by Virgin Media. By December 2007, Sky had been told by the Competition Commission to cut its stake in ITV, and the then business secretary, John Hutton, upheld the ruling.

In a legal process that involved the competition appeals tribunal and the court of appeal and six QCs, Sky did not agree to relinquish its holding until February 2010. A similar process would see News Corp battling for Sky until 2014, although such a long fight would be politically fraught. News Corp still faces ongoing scrutiny by Ofcom, which was asked on Monday by Hunt to look again at whether Sky's owners are "fit and proper" persons to hold a broadcast licence.

A spokesman for Ofcom said the regulator would give its view in due course, and its chief executive, Ed Richards, would be writing to the police, the Press Complaints Commission and parliamentary select committees to ask to be kept abreast of any new information.